Method and apparatus for treatment of waste paper stock



Nov. 4, 1958 M. EQ SANFORD METHOD AND APPARATUS FOR TREATMENT OF WASTEPMs-ER STOCK Filed March 2e, 195ev m .EH w

INVNToR. MARCUS f. SANFORD .Jya. Www

AT1-ORNE v5 United States Patent NIETHOD AND APPARATUS FOR TREATlVIENT YPAPER STOCK Marcus E. Sanford, San Francis/co, Calif., assignortoFibreboard Paper Products Corporation, a corporation of DelawareApplication March 26, 1956,Seria1 No. 573,981

11 Claims. (Cl. 92-'20) avoid undesirable consequences of wax spots onthe sur-V face of nished paper.

In the manufacture of paper, particularly lower grades of paper such asused as liners for corrugated paperboard, extensive use is made of wastepaper as a sourceV of pulp stock. In such processes, waste paper iscollected, disintegrated in conventional beaters which a-gitate it in aturbulent liquid bath to render it into a fiber containing slurry; largeforeign objects which are inevitably present in waste paper are removedand the slurry is then further refined to deiiberize or debrate it tobreak up ber agglomerates and separate the individual iibers. 'Iheslurry is then usually screened to remove residual foreign particles andused as stock for paper making in accordance with conventionalprocesses.

Although the foregoing prior process has been in use for some time, itis still not all that is to be desired for a nunber of reasons. In therst place, waste paper inevitably includes some wax-bearing papers; andthe wax, which is not separable from the stock by usual methods such asscreening, eventually appears as spots on the surface of iinished paper.Wax spots are objectionable because they detract from appearance of thepaper and also adversely affect its amenability to printing or gluing.Consequently, such wax is a cause of rejection or downgrading of muchiinished paper and so poses a serious economic problem.

To minimize the wax problem, current practice is to specify that wastepaper be free of wax or waxed paper. Consequently, waxed paper is a drugon the market as it is not usable for paper production in accordancewith previously used methods. tied tobe wax free, waste paper invariablycontains some waxed paper which cannot be economically sorted out byhand and which contributes to the above mentioned rejection ordowngrading of iinished paper.

Another problem of the above described prior process lies in removal ofsmaller foreign material such as asphalt akes, small mortar flakes ordirt, etc. In accordance with conventional practice in the abovedescribed prior processes, slurry from which relatively large foreignobjects have been removed is debrated or reiined, usually between tworelatively moving opposing discs, or `concentric cones as in the wellknown Jordan machine, to break up agglomerates of bers.

This refining operation separates fibers and at the same time releasesor separates relatively small foreign materials entrapped inagglomerates of fibers. The relined slurry is then screened to removeseparated foreign materials. However, removal of foreign materials inthe Moreover, even though speci- Patented Nov. v4, 1958 screeningoperation is often inadequate because the usual deibrating methodslemployed in the `above described prior processes grind the foreignmaterials into ne par` ticles. The result is that at least part of suchforeign materials are reduced to the same size range as the paper fibersso pass through the screen with them and eventually show up in thefinished paper. troublesome in this respect because it s usually presentin the slurry as flakes which are broken up in the usual debrator intovery smallpieces which readily pass through the screen with the fibersand so are present in finished paper.

In summary, the present invention overcomes the above mentioneddifficulties of prior processes and to that end provides ways land meansfor avoiding the deleterious ef-A fects of wax in waste paper which isused for subsequent formation into paper, thereby enabling the use ofcheaper grades of waste paper and eliminating the necessity for handsorting. The invention also provides an improved system for deibratingor refining paper pulp whereby desired separation or reduction ofagglomerates of fibers Vis accomplished without grinding of eitherfibers or forobjectionable by treating waste paper stock in a particularAsphalt is particularly manner under controlled conditions to effectdispersion of wax uniformly throughout such stock on the bers thereof,thus preventing its appearance asfspots on the iinished paper. This isaccomplished by forming a slurry of the waste paper stock and thendewatering the slurry to form a thickened pulp in which substantiallyall water is absorbed in the cellulosic fibers. Such thickened pulp isin the form of a'kneadable mass containing substantially no non-absorbedor free water in contradisrtinction to a slurry or suspension of thefibers in Water; Suchl thickened pulp is of high consistency compared tothe lower consistencies of paper iibers in a slurry or suspen sion inWater. For reasons explained more fully hereinafter the advantagesl ofthis invention cannot be obtained by handling low yconsistency paperslurry or suspensions. The thickened pulp of this invention should be ofa consistency of at least about 20% for best results, and desirablyhigher. sistency is calculated as (weight of dry solids in pulp/ totalWeight of wet pulp) X 100.

After forming lsuch thickened pulp, it is heated to a temperature abovethe melting point of waxes to be disdesirably simultaneously agitatingthe same Vto insure thorough mixing and thereby thorough heating andthus enhance dispersal of melted wax therethrough. The re# sultant massis then deiiberized or deiibrated by a kneading action without grindingindividual fibers or breaking This is so, because at lowerconsistencies, say below' about 15% solids, there is so muchliquidrpresenttht As used in this specification, con.-

V persed but below the melting point of higher melting impurities, suchas asphalt, contained in the pulp, while most of the wax upon heatingwill melt and either form a relatively dilute emulsion or float on thefree water, and Vis not eiciently contactedby the fibers. Consequently,.a large proportionofV the wax will .-not-be;unif: formly deposited on`fibers and. will, upon` subsequent] cooling ofthe stock, be depositedrandomly on fibers andthusshow up as wax spots onnished paper. Morer'over, free wax may cool and solidify on equipmentithuscausingundesirable waxV buildupsand necessitating,` shut down'for cleanout.`Suchcleanout isrequired because relatively largeA pieces of suchsolidiiedwx may break away and eventually-show up asvspots on nishedLpaper.

At. consistenciessabove Yabout %,Y thereis no free water unabsorbed bythe fibers andk so the melted wax.

is brought into efiicient contact with the fibers for dispersaluniformlylthroughout therentire mass of pulp. As a result, papermadefrom -such pulp-will have no im perfectionsdue to` wax spots'onthesurface.

In this connection, it is lto be notedA that the meltedV wax isapparently taken up primarily by deposit on sur? agitation is attainedconcomittantly with heating by mov-` ing the pulp through a screwconveyer during such heating. Y

As to maximum consistency of the pulp during the wax dispersal step,this is relatively unimportant insofar as functional eect concerningdispersal of the wax is concerned. Higher consistencies do however offeran economic advantage in heating in that in higher con` Vsistency pulpthere is less water to absorb heat. ever, the consistency should not beso high as to render Howthe pulp dicult to handle in currently availableequipment." A consistency of a maximum of about 50% Vis ashigh as is isVto be obtained by employing higher consistencies.- It should be noted,however, that higher consistencies in the range noted should be employedfor higher waxA content pulp as that will make the wax dispersal moreetlicient, because the higher the consistency the better the dispersalof the wax.

Heating of thickened pulp to disperse wax may be accomplished by anysuitable method and by either direct,

or indirect heating. However, direct heating by injecting saturatedsteam (212 F.) into the thickened pulp is desirable because of itseconomy and efficiency and also because such steam injection into pulpas it Vis agitated, as in a screw conveyer, will also contribute someagitation as well as insure more efficient heating.

waxes, which have relatively low melting points (1201. 2009 Fu), aremelted and dispersed. Impurities, such as asphalt, which have muchhigher melting points are deliberately left in the unmelted or solidstage, or'inV other words as discrete solid particles, so that they arenot dispersed into the bers and Vare Vamenable to physical removalmethods, such as subsequentscreening.

It is important that the entire thickened pulp mass be thoroughly heated'throughout to insure substantially complete meltingrof thewax. Allobsel'vationsindicate.; that the wax dispersesrsubstantiallyimmediately' as it is melted provided the pulp is of a consistency above20%; the uniform dispersal being facilitated by simultaneous agitationYofy the pulp with the heating thereof. Thus, there is no need Vformaintaining the pulp at final wax Vmelting temperature for anyparticular time period after the entire mass of pulp has reachedsuchtemperature. In this connection it is noted that the Ytime required tobring the entire mass of pulp toV wax dispersing tempera-il Y- ables,including the size lof equipment, quantityA of pulpj and quantity ofheat added per unit of time. However; 1 1' in most cases, usingequipmentV of the type hereinaftei'j:V

ture is not critical and will depend upon several-'vari described, suchheating may be accomplished inY from'2: i to 60 seconds and so'theprocess is very eicientfromfa-V l' time standpoint. v Y l Thetemperatures employed are suchy that'theA melting points of -the highestmelting waxes toebe dispersedy are ex;

pulp.

types of waxes, the pulp is heated'to a temperatureiiijtf"fY Due to therelatively low temperaturesrequired by Y the invention, Vas hereinafterdiscussed, relatively little steam is required to effect heating and sothe quantity of moisture introduced by the steam is negligible and willnot materially lower the consistency of the thickened pulp.

However, if because of local conditions there is danger of diluting thepulp too much, then it can be initially i thickened to a higherconsistency, or non-diluting heating means employed. Y

In connection with heating of the pulp, it is to be noted that it isaccomplished at substantially atmospheric pressure, thus enabling theuse of ordinary saturated steam (212 F.) and also avoiding problems andatmospheric pressure, thus enabling the use of ordinary saturated steam(212 F.) and also avoiding problems and expense attendant upon usingsealed equipment in which pressured steam or gas is employed. The use ofrelatively low temperature and non-pressured apparatus is possibleV withthe present invention becauseonly the VAKline waxes havel melting pointsin the'range fromV 110-V i ceeded; In general, waxes present in wastepaper arerriix;I j turesof crystalline wax, Vsuch as used in Vwaxedpaper-,f and higher melting micrdcrystalline waxes-.employed .7- forspecial uses to withstand hightemperatures. Crystal' F. whilemicrocrystalline waxes have vmelting points up to'about 2G09V F.YTemperatures tobev employed inf processing pulpV in accordance with thisinvention'gwill" depend primarilyY upon the type of wax presentfinrtheffHowever, to insure `substantial dispersal offalljA the range from aboutF. to 200 F; Ifit'isknolwn that microcrys'talline waxes are absent fromvtheV pulp,`

then lower temperaturesrto disperse only crystalline waxes j' may beemployed. The relative quantity of total wax presentin, the pulp@V stockis not a practical factor inthis invention because g tests havedemonstrated that pulp containing. asmuch as 15 by weight wax (drybasis; pulp solids to wax) can be effectively treated in accordance withVthe invention. Waste paper consisting of 100% waxed paperconf tainsonly about 10% wax by weight. Thus, it is ,ap-Y parent that the usualwaste paper, which is a mixture of waxed and unwaxed papers', willcontain` less than about.` 10% wax, consequently the invention can beemployed to eciently cleanse waste paper pulp stock made Yfrom any wastepapers currently extant sincenone of them will exceed 10% wax and theprocess can handleY at least 15% Wax.

When the wax has been dispersed by heating as above` described, the pulpisY then subjected to a particular re-. V- ning or debrating operationinwhich the fibers are separated into substantially individual fibersy to.prepareV the pulp for use in paper formation, but without uncle-s1vsirable grinding or breaking up of foreign particles. A In` i otherwords, the pulp is refined: to Vreduce ber agglomerates or separatefibers while leaving foreign ma-` f terials in a substantially ungroundnor unreduced state.y Also such particulardefbration, which'is a combingor kneading action does not grindy up individual fibers. Grinding offibers is undesirable because extremely ,shortY fibers do not properlyinterlace and` mat in subsequent paper making. Y Y

Thus, in accordance with ar feature of vthis invention, Y the pulp isdeiibrated by a kneadingl orcombingaction` between spaced apart members,such as-between spacedtA apart pins or lingers which rotate or otherwisemove at VVof fibers into'individual fibers.

high speed relative to each other but without engage- .ment with eachotherrand thus pull -apart agglomerates Since the debrating members arespaced apart and do not engage each other,

there is no grinding of individual fibers or-'foreign particles.

When properly defibrated, the bers are of a much ner and smaller sizethan most of Athe foreign particles and upon dilution lof the debratedApulp to vforman aqueous slurry or suspension, they can be Vreadilykseparated from the foreign particles by known means such .as screensand the like. In this connection, if

. the Vpulp consistency istoo low so that there is excess unabsorbedWater, the mass cannot be debrated without also grindingup the foreignparticles. Hence the thick pulp is` also important to permit defbrationby the described combing or kneadingaction which results in thedeibration .as a .result of friction between the fibers, .and does sowithoutA breaking up theA larger foreign particles.

Reference is made to the .accompanying drawings which form amaterialpart of this specification and .Whichillustrate a preferredembodiment of the invention. It is to be understood, however, that theembodiment described hereinafter is for purposes of illustration.only-and is not to be considered as limiting this invention since thescope thereof is defined by the appended V claims.rather than by thedescription preceding. them.

In the drawings: ,Fig 1 is a more or less schematic elevational v1ew,

partly. in, section, .of a formofa stock. cleaning system ,embodying theinvention. .Fig...2,is.a fragmentaryelevational. view,;partially 1nsection, .of a. debrating machinefor refining ordeflbratingV pulp in..accordance. with the invention.

Fig. 3 is an ,enlarged partial section of the right hand side of themachine shown in. Fig. 2, illustratingu the ,opposing sets of pins inmore detail.

In the system shown in'Fig. l which embodies conventional equipmentunits, Waste paper bales are broken up 'and the paper rendered into adilute slurry in a convenof saturated steam injecteddirectly intohousing 21 of the waxl dispersal unit through valved steam lines 27Vtopermeate and heat lthe pulp as it passes therethrough. Such housingis not Asealed because the heating is accomplished at substantiallyatmospheric pressure. In this connection, itwill be noted that othertypes of conveyor and other heating means may be employed. However, itisdesirablethat the conveyor and heating means be such that agitation ormixing of the pulp occurs during heating" so that uniform heating andthorough dispersal of wax will be attained simultaneously.

The thickened and heated pulp, which now has its wax content disperseduniformly throughout its mass,

' is conveyed by means of vertical conveyor 25 to gravity dischargethrough a conventional chute 28 into the debrating machine 26"which isdriven by a suitable motor 29. In such defribrator the pulp is subjectedto a kneading or combing action which is accomplished in the embodimentillustrated by'means of two opposing sets of pins 30 Aand 31 one ofwhich `rotates with respect to the otherto effect kneading of the pulpby a combing action .as it'passes radiallyl (i. e. ina directiontransverse to movement of the pins) from the inlet 32 at the uppercentral portion-.of'deibrating machine 26 to the periphery thereofwhence it is discharged (Figs. 2 and 3).

The refined and defibrated pulp `passes through conduit 33 into aconventional dilution tank 34 in which :than labout-,2%

it is suitably diluted yto a .dilute suspension capable of subsequentscreening, usually of a consistency of less However, in this connection,the pulp may bediluted to any consistency inWhich thereis su- Vtofurnisha discharge zone 38A from which diluted stock may be discharged,via conduitv 39, in to a conventional screen 41 in which residualforeign material is removed from the pulp. .Screened product stock isdischarged from' screen41 through .a conduit 42 to further processtional'breaker-beater or Hydrapulper 11 which hence ',provides a supply sourcefor the remainder of the system. The pulp is then passed through aconduit 12 Vinto Qa headbox 13. Consistency of the. pulp `as received inAthe head box is usually inthe range of 1% to 4% solids. Ihe head box isprovided with usual baffles 14 to minimize turbulence therein anddeliver the slurry at a controlled volume Athrough conduit 15 into athickening or ,dewatering press 16. Such .press 16 is of conventionaldesign suitable for thickening or dewatering pulp toa consistency in therange from 20% to 50%. The press illustrated, which may be of any well.known type, is a screw press, driven in a conventional manner throughgear box 17 by means of a suitable motor (not shown).

Thickened pulp is discharged from the bottom .of the 4press by means ofan internal screw discharge (not shown) and scraped by Scrapers drivenin conventional Vmanner by motorlS, to drop into and through a chute v.19 into a Vwax dispersal unit 20 which includes .a housing 21 and ahorizontal screw agitating conveyer 22 within the housing Where it isheated kas hereinafter described. The conveyor is driven by a suitablemotor 23. Liquid extracted from pulp in the press is discharged inconventional manner through conduit 24 and returned to process ordiscarded.

Horizontal screw conveyor V22 agitates the pulp while conveying itthrough the wax dispersal unit 20 .to a vertical screw conveyor 25,driven by a suitable motor (not shown) and which delivers the pulp to adebrating machine 26. Y In order to disperse wax, the pulp is heated asit passes through horizontal screw conveyor 22, suicient heat beingadded to bring the pulp to a temperature above the melting point of thewax.

In the embodiment shown, heating is done by means ing in accordance withconventional practice for forming paper from refined stock. Foreignparticles are discharged from such screen 41 through conduit 43. Withrespect to the screening operation, this is a desirable step to removeforeign particles, however, if the waste paper stock is relatively freeof foreign-particles7 or if the presence of such foreign particles inthe final paper is notobjectionable, then the screening may be omittedas the preceding Wax dispersal step will have dispersed the wax. Also,if the screening is omitted, prior debrating machines may be employedwhich grind for- However, the use of the kneading or combing method ofdebrating of this invention is desirable in any case as itavoidsundesirable grinding of individual fibers.

Figs. 2 and 3, illustrate details of a preferredtype of deibratingmachine 26 for use in the system illustrated in Fig. l. In theconstruction shown, pulp enters a chamber 4.4 of themachine at theupper. central portion thereof through feed inlet 32 and passes onto theupper surface of arotating plate'46 on which is mounted one set of pins31. Due to centrifugal force generated by the rotation of plate 46 thepulp is thrown radially outwardly, thus causing it to pass through anetwork formed by two opposed series of pins, one series of which 31 isattached to plate 46 to rotate therewith and the other .series 30 isattached to a xed top surface A47 of the chamber 44. In this connection,it will be noted that the pins are spaced apart and substantiallyparallel thereby forming comb like teeth that do not engage or toucheach other as disc 46 rotates.

spaced apart pins effectively breaks up any lumps ork Y agglomerates offibrous material and so eciently refines such-material to a statesuitable for forming into paper in accordance with conventionalpractice.

As pulp reaches the periphery of chamber 44, vanes 48 mounted on theperiphery of rotating disc 46, act

as impellers to discharge defibrated pulp through a discharge outlet 49connected to a conduit, such as conduit 33 of Fig. 1, leading to aconventional vdilution tank.

It will be noted that the pins are positioned with respect to each otherso there is substantial space therebetween and upon rotation of disc 46the series of pins 31 fastened thereto doV not contact or intermesh withthe opposite series of pins mounted on the top 47 of chamber 44. This isimportant because if the pins are too close together there will be agrinding of both fibers and foreign materials. This may result in lossof pulp `in subsequent screening. Further, such grinding action willalso reduce the size of foreign materials to the same size range as thefibers in the stock, thus renderingit impossible to remove such foreignmaterials from the pulp stock by screening. Y

Although for removal of foreign particles or refining of pulp withoutgrinding the individual fibersl the embodiment illustrated employs adebrating machine which utilizes pins to effect kneading or combing ofthe pulp without grinding, it is to be understood that other equivalentmachines may' be employed to accomplish the same purposes.

As above noted, debrating machine 2 6V is driven in a conventionalmanner by means of a suitable motor 29 connected thereto in such amanner as to rotate a shaft 51 upon which the disc 46 is mounted.

Equipment of the type useful in the present invention may be of anydesign suitable to accomplish the desired purpose. Thus, the press maybe a Model ZL Zenith Press; the screw conveyor used as a wax dispersalunit may be of any standard make and may be insulated if desired foreconomy; and the defibrator may be a Model 015 Roto-Pulper. Forscreening, several machines are available. A typical screen for such useis the Bird Screen Model L-40.

As noted above, consistency of the stock entering the press 16 isusually in the range from 1% to 4%, however operation of press 16 isenhanced if the entering stock has a consistency above about 2%. In theembodi` ment illustrated, a preliminary dewatering of stock to insuresuch a consistency is simply accomplished by means of a sloping screen52 over which stock falls as it overflows weir 14 to enter conduit 15.Water gravity drains fromv the stock through such screen and is recycledto the breaker-beater or to other use through suitable conduit 53.

Example 1 In a pilot plant, a system corresponding generally to Fig. lwas employed, the breaker-beater and head box were conventional in allrespects. A Zenith press, manufactured by Jackson and Church Companyhaving a capacity of 8O tons of pulp solids (dry basis) per 124 hours,was utilized to thicken the pulp to the desiredV having a capacity of 75tons of solids (dry basis) perv 24 hours was used to refine thethickened pulp after heating thereof.

Over a 30 day period of operation of the abQve sys- 75 `occurs due tothe kneading action therein.

ples were cast into hand sheets in accordance with stand- Vardlaboratory practice and compared. The sheets cast tem, waste paper stockhaving an average Wax content of 2.5% by weight (dry weight) wastreated. Average rate of stock throughout was 60 tons pulp (dry weight)per 24 hours. On some occasions stock throughput dropped to 41 tons per24 hours and on others was as high as tons but such variations did nothave `any deleterious effect on the process.

Consistency of the stock as it entered the Zenith press during suchperiod ranged from 1.64 to 4.04%; and consistency of thickened pulpdischarged from such press was in the range from 33% 'to 46%.Temperatureof thickened pulp leaving the horizontal conveyor 22 was inthe range from F. to 195 F. and heating to such temperature wasaccomplished by injecting steam at 212` F. and atmospheric pressure intothe pulp at spaced intervals as it passed through the wax dispersalunit.V Time of pulp residence in such unit ranged from about 20 secondsto about 50 seconds. Periodic samples were taken of heated pulp as itleft the conveyor and such samples were cast into paper sheets in thelaboratory. In all cases the waxr was' completely dispersed in the paperand objectionable wax spots were missing..

After Wax dispersal, the stock was debrated, diluted and screened in amodel L-,4O Bird Screen. Non-fibrous impurities removed in thescreenaveraged about 7 pounds per ton of pulp (dry weight) and includedthe following:

.Percent- Asphalt 40 Cellophane 30 Sticks and straw 2 Foil Food and misc5 The asphalt was in the form of akes and the other.

material was in a suitably unground state for ready removal from thepulp, thus demonstrating the eciency of the debrating method employed.

Stock discharged from the screen was fed to a paper making machine onwhich it was formed into top grade paperboards, the surfaces of whichwere free frornwax and readily amenable to printing, gluing and otheruses. None of the paper produced from pulp stock treatedin accordancewith the invention was downgraded or discarded because of Wax on Vitssurface.

Example II During the operation described in Example I special testswere conducted to demonstrate the wax dispersal efficiency during steamheating in the horizontal screw` weight) of added wax in the pulp.Temperature in the` conveyer was maintained at F. by introduction ofsaturated steam. Pulp throughput rate was 50 tons (dry weight) per 24hours and total residence time in the conveyer was about 45 seconds.

Samples were collected of heated thickened pulp discharging from the waxdispersal unit before such pulp entered the deberizer. Samples were alsotaken of pulp discharged from the deberizer where further agitationThese samfrom the pulp samples taken directly from the Wax dispersalunit showed as complete dispersal of the wax-dye mixture as did sheetscast from the deiiberized pulp, thus ldemonstrating the efficiency ofthe heating method 4of the-invention whereby wax dispersal isaccomplished by thorough heating, as physically evidenced by the uniformdispersal of the above wax-dye mixture during the heating.

.Since the wax was as thoroughly dispersed in the pulp 9 before thedebration step as it was after such step, the tests demonstrate thatagitation is unnecessary after heating provided the pulp has beencompletely and thoroughly heated throughout. As noted above, thoroughheating is enhanced by agitation during such heating. However, agitationmay be done after the heating if desired, but this is not too desirableas it lowers the eiiiciency of heating.

I claim: v

1. The method of treating ber containing stock for the production ofpaper which comprises forming a mickened pulp of such stock, heatingsuch thickened pulp at a temperature Vsuiiicient to disperse wax thereinbut below the temperature at which asphalt is lmelted and dispersedtherein, combing the wax dispersed thickened stock to defibrate the sameby friction between the fibers Without effecting substantial breaking upof foreign particles in the pulp, diluting the thus defibrated pulp toprovide an aqueous suspension thereof from which said foreign particlescan be removed, and removingl such foreign particles from thesuspension.

2. The method of treating wax-bearing waste paper stock containing solidimpurities larger than individual fibers of said stock prior toformation of such stock into paper, comprising thickening said stock toa pulp having a consistency in the range from to 50%, heating saidthickened pulp to a temperature above the melting point of waxescontained therein and below the melting point of higher meltingVimpurities contained therein, agitating said pulp while heating thesame, refining said pulp by combingto reduce agglomerated fibers whileleaving larger impurities substantially unreduced and to separate saidbers from said largerV impurities, diluting said refined pulp to form aslurry and removing said larger impurities from said slurry ofreiinedpulp by screening.

3. The method of cleaning paper stock formed from waste paper andcontaining as impuritieswax and solid foreign particles relativelylarger than fibers of said paper stock, comprising pressing said stockto form a pulp mass of a consistency above about 20%, heating said pulpat a temperature sufficient to substantially melt wax contained thereinbut below the temperature at which asphalt is melted, agitating saidheated pulp to disperse said melted wax uniformly throughout the mass ofsuch pulp, refining said pulp to deiibrate the same to reduceagglomerates of bers therein while leaving substantially unreducedtherein said relatively larger foreign particles by kneading said waxdispersed pulp between moving spaced apart pins to thereby substantiallyseparate said unreduced relatively larger foreign particles from fibersof said pulp, and removing said separated unreduced relatively largerforeign particles from said refined pulp stock by diluting and screeningthe same.

4. The method of refining waste paper stock containing solid foreignparticles which comprises thickening said stock to form a pulp in theform of a kneadable mass containing substantially no free water, andkneading said thickened pulp to debrate the same by friction betweenfibers to reduce agglomerates of fibers and leave individual fibers andsaid solid foreign particles substantially unreduced.

5. The method of treating waste paper stock containing solid foreignparticles relatively larger than fibers of said stock for forming intopaper, which comprises thickening said stock to a pulp having aconsistency above about 20%, combing said pulp to debrate the same andseparate said relatively larger foreign particles therefrom, andsubstantially removing said relatively larger foreign particles fromsaid refined stock by diluting and screening said stock.

6. The method of cleaning waste paper stock containing as impurities waxas well as solid foreign particles having a melting point higher thansaid wax and of a size relatively larger than fibers of said stock,comprising thickening said stock to form a pulp of a consistency forabsorbing melted wax, heating said thickened pulp in a zone unsealed tothe atmosphere to a temperature for melting said wax and below themelting point of said relatively larger foreign particles by injectingsteam at substantially 212 F. into said pulp stock in said zone,agitating said pulp in said zone during heating thereof to substantiallydisperse melted wax on fibers of said pulp stock, refining said pulpstock after heating and agitation thereof to effect substantialdeiibration thereof and substantial separation of fibers from saidrelatively larger Vforeign particles, and removing said separatedrelatively larger foreign particles from said pulp stock by diluting andscreening said pulp stock.

7. Apparatus for treating waste paper stock containing wax,comprising-means for thickening said stock to form a pulp of aconsistency above about 20% for absorbing melted wax, a chamber unsealedto the atmosphere for receiving said thickened pulp, means for injectingsteam at substantially 212 F. into said chamber to heat said pulptherein to substantially melt its contained wax, means for agitatingsaid pulp duringheating thereof to effect uniform dispersal of meltedwax, and combing means for defibrating the pulp after said waxdispersal.

8. Apparatus for cleaning waste paper stock containing wax as well asforeign particles having a melting point above that of said waX and of asize relatively larger than bersof said stock, comprising a source ofsupply of said stock, means for thickening said stock to a pulp of aconsistency for absorbing melted waX, means unsealed to the atmospherefor simultaneously agitating said thickened pulp stock while heating itto a temperature to substantially melt said wax, combing means forrefining said pulp after said heating and agitation to defibrate thesame and effect substantial separation of bers thereof from saidrelatively larger foreign particles, and means for diluting andscreening said pulp stock to remove saidscparated foreign particlestherefrom.

9. In the method of treating waste paper stockV containing waX andasphalt impurities, the steps Vcor'nprising forming a thickened pulp ofsaid stock, and heatingV said thickened pulp at a temperature sucient tomelt substantially the waX contained therein but below the temperatureat which asphalt is melted to thereby leave asphalt in the pulp asdiscrete solid particles.v

10. The method of treating waste paper stock containing waX and asphaltimpurities and also solid foreign particles which comprises forming athickened pulp of said stock in the form of a kneadable mass containingsubstantially no free water, heating said thickened pulp at atemperature suicient to melt substantially wax contained therein butbelow the temperature at which asphalt is'melted to thereby leave theasphalt in the pulp Yas discreet solid particles, refining said pulp bya combing action without grinding-the same to reduce agglomerated bersWhile leaving substantially unreduced therein said solid foreignparticles and said asphalt, diluting said refined pulp to form a slurry,and screening such slurry to remove solid foreign particles andunreduced asphalt.

11. The method of claim 9 wherein the thickened pulp is heated atatmospheric pressure by steam and is Vsimultaneously agitated during theheating. v

References Cited in the le of this patent UNITED STATES PATENTS1,773,055 McDougall Aug. l2, 1930 1,833,852 Osawa Nov. 24, 19312,116,511 Earle May 10, 1938 2,142,823 Nickerson et al. Ian. 3, 19392,592,215 Wandel Apr. 8, 1952 2,697,661 Hollis Dec. 21, 1954 2,718,178Wandel Sept. 20, 1955 FOREIGN PATENTS 689-21@ I .Greatnritain Masas,i953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,859,110 November A, 1958 Marcus E. Sanford It iis hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as correcte'd below.

Column 3, line 42, after "is", first occurrence, insert practical withcurrently available equipment. However, since substantially complete Waxdispersal occurs at consistences in the range from 20% to 50%, no Waxdispersal advantage lines 69 to 72, strike out "at-mospheric pressure,thus enabling the use of ordinary saturated steam (212O E.) and alsoavoiding problems andf; column A, line A, for "stage" read state linesl9 rand 20, strike out Htempr-zra-ables'," and insert insteadtemperature is not critical and Will depend upon several variables, line23,r strike out "ture is not critical and' Will depend upon severalvariJ'.

Signed and sealed this 23rd day of June 1959.

(SEAL) Attest:

KARL H., AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

1. THE METHOD OF TREATING FIBER CONTAINING STOCK FOR THE PRODUCTION OFPAPER WHICH COMPRISES FORMING A THICKENED PULP OF SUCH STOCK, HEATINGSUCH TICKENED PULP AT A TEMPERATURE SUFFICIENT TO DISPERSED WAX THEREINBUT BELOW THE TEMPERATURE AT WHICH ASPHALT IS MELTED AND DISPERSEDTHEREIN, COMBING THE WAX DISPERSED THICKENED STOCK TO DEFIBRATE THE SAMEBY FRICTION BETWEEN THE FIBERS WITHOUT EFFECTING SUBSTANTIAL BREAKING UPOF FOREIGN PARTICLES IN THE PULP, DILUTING THE THUS DEFIBRATED PULP TOPROVIDE AN AQUEOUS SUSPENSION THEREOF FROM WHICH SAID